1. Field of the Invention
The present invention relates to a method of classifying fine particles and, more particularly, to a method of classifying fine particles contained in fine particle dispersion by using a micro flow channel. Also, the present invention relates to an apparatus of classifying fine particles and, more particularly, to an apparatus of classifying fine particles contained in fine particle dispersion by using a micro flow channel.
2. Description of the Related Art
Methods of classifying fine particles include a dry classification method and a wet classification method.
The dry classification method may have high precision due to a large difference in specific gravity between the liquid and the fine particle.
On the other hand, according to the wet classification method, the difference in specific gravity between the liquid and the fine particle is small. However, the fine particles are easily dispersed in the liquid. Thus, high classification accuracy is obtained, especially, in a fine particle-size region. In both the dry classification method and the wet classification method, usually, a classifier has a rotary part. Further, it is a main stream approach to classify fine particles by utilizing the balance between a centrifugal force and an inertia force. However, due to the presence of the rotary part, related classifiers have problems of wear contaminants and cleaning thereof. A classifier for the dry classification method, which utilizes “Coanda effect” without a rotary part, has been commercialized. However, no classifier enabled to efficiently perform the wet classification method without a rotary part has been obtained.
Meanwhile, various methods of performing chemical reactions and unit operations in a micro-region have recently been studied. Methods and apparatuses of efficiently classifying fine particles without producing contaminants have been studied.
“Development of Method of Continuous Classification of Fine Particles Using Laminar Flow System in Microchannel”, Proceedings of 69th Annual Meeting of the Society of Chemical Engineers, Japan, No. 201 has proposed a method and an apparatus of using a microchannel having a partly thinned part (a pinched channel) and utilizing the profile of a characteristic flow in the microchannel, so that fine particles in a direction perpendicular to the flow can be classified only by introducing the fine particles, as a method and an apparatus of classifying fine particles. This document has reported that this method can classify fine particles having diameters of 15 μm and 30 μm.
“Study on Behavior in Micro-Separator/Classifier by Euler-Lagrange Method”, Proceedings of 69th Annual Meeting of the Society of Chemical Engineers, Japan, No. 202 has reported a method of separating and classifying fine particles by utilizing the difference in specific gravity between a fluid and a fine particle and also utilizing a centrifugal force and a lift force, which relate to the flow rate of the fluid, in a circular-arc-like microchannel that is rectangular in cross-section.
However, the former method, which classifies fine particles without utilizing a force of gravity and a centrifugal force, has problems of the settling and the sedimentation of fine particles onto the bottom surface of the channel in a case where the specific gravity of the fine particles is larger than that of a fluid. On the other hand, the latter method utilizes a centrifugal force and has good performance of classification in a case where the difference in specific gravity between the fine particle and the fluid. However, the settling of the fine particles is also facilitated. Thus, it is difficult to achieve both of the enhancement of classification efficiency and the prevention of the sedimentation of the fine particles and the blocking-up of the channel.
Both of the former method and the latter method have a problem that an amount of sediment increases and the flow channel is blocked up in a case where the classification is continuously performed for a long time.